US: Ecologists have long sought to explain the distribution patterns of species diversity, which is an increasingly important research goal as climate change is expected to alter these patterns considerably. A team of researchers from US in a paper published on IOP Science portal have now established the relative importance of climate and vegetation properties on patterns of North American breeding bird species richness.

“Canopy vertical structure, measured using LiDARdata from a satellite, was not as important a predictor of bird species richness at the national scale as we would have expected based on results from more local to regional-scale studies,” Scott Goetz of Woods Hole Research Center, US, said. “That indicates to us there are important differences driving species richness patterns across spatial scales.”

It’s useful to look at the large-scale patterns of bird life as both land use and climate change; recent advances in remote sensing and ecological modelling have made this possible. As a starting point, Goetz and colleagues used data from the Breeding Bird Survey to build up a model of species richness across the US for four guilds of birds that like to use particular habitat for breeding – forest, grassland, open woodland or scrub/shrub.

For the ecological variables that affect this species richness, such as climate, topography, vegetation properties and canopy structure, the team employed a mix of sources, including the WorldClim data set, the Shuttle Radar Topography Mission collection 4 data set, the SYNMAP global land cover map, MODIS Enhanced Vegetation Index and satellite-based LiDAR data from GLAS – the GeoScience Laser Altimetry System onboard NASA’s ICESat.

Other studies using airborne, rather than satellite, LiDAR have found moderate to strong relationships between vegetation canopy structure and species richness. However, airborne LiDAR data are generally only available over small areas.

Figure 1: Distribution of BBS routes throughout North America and the number of GLAS LiDARshots within 200 m of each route (upper left). The inset details the locations of the GLAS shots (right) and the histogram shows their height (m) distribution (lower left).

“It is quite possible that LiDAR measurements of canopy structure at the national scale would have been more important predictors – and allowed us to improve the models and maps even further – had we been able to use high-quality LiDAR data from aircraft,” said Goetz. “Currently though, all we have available to work with are lower-resolution data from a sampling LiDAR instrument originally designed for studying ice sheets, and that sensor stopped operating in 2009.”

The researchers would like to further advance mapping biodiversity habitat in the context of continual change. Goetz, however, added, “A space-based instrument is the only way to acquire systematic measurements over large areas. Having such data sets would advance ecosystem models of biodiversity as well as carbon cycling and many other aspects of the integrated Earth system.”